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Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
(Q)SAR
Adequacy of study:
weight of evidence
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
results derived from a valid (Q)SAR model and falling into its applicability domain, with limited documentation / justification
Justification for type of information:
The supporting QMRF report has been attached
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Principles of method if other than guideline:
The data is predicted using the OECD QSAR toolbox version 3.4with logKow as the primary descriptor.
GLP compliance:
not specified
Specific details on test material used for the study:
- Name of test material: Pyrazine-2-carboxylic acid
- Molecular formula: C5H4N2O2
- Molecular weight: 124.099 g/mol
- Substance type: organic
- Physical state: solid
- Smiles: c1ncc(C(=O)O)nc1
- InChI: 1S/C5H4N2O2/c8-5(9)4-3-6-1-2-7-4/h1-3H,(H,8,9)
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Test temperature:
21 Deg.C
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
145.27 mg/L
Nominal / measured:
estimated
Conc. based on:
test mat.
Basis for effect:
growth rate

The prediction was based on dataset comprised from the following descriptors: EC50
Estimation method: Takes average value from the 5 nearest neighbours
Domain  logical expression:Result: In Domain

(((((((("a" or "b" or "c" or "d" )  and ("e" and ( not "f") )  )  and "g" )  and ("h" and ( not "i") )  )  and "j" )  and "k" )  and ("l" and ( not "m") )  )  and ("n" and "o" )  )

Domain logical expression index: "a"

Referential boundary: The target chemical should be classified as Aryl OR Carboxylic acid OR Pyrazine by Organic Functional groups ONLY

Domain logical expression index: "b"

Referential boundary: The target chemical should be classified as Aryl OR Carboxylic acid OR Overlapping groups OR Pyrazine by Organic Functional groups (nested) ONLY

Domain logical expression index: "c"

Referential boundary: The target chemical should be classified as Acid, aromatic attach [-COOH] OR Alcohol, olefinic attach [-OH] OR Aromatic Carbon [C] OR Aromatic Nitrogen OR Carbonyl, olefinic attach [-C(=O)-] OR Carbonyl, one aromatic attach [-C(=O)-] OR Miscellaneous sulfide (=S) or oxide (=O) OR Olefinic carbon [=CH- or =C<] by Organic functional groups (US EPA) ONLY

Domain logical expression index: "d"

Referential boundary: The target chemical should be classified as Aromatic compound OR Carbonic acid derivative by Organic functional groups, Norbert Haider (checkmol) ONLY

Domain logical expression index: "e"

Referential boundary: The target chemical should be classified as No alert found by DNA binding by OASIS v.1.3

Domain logical expression index: "f"

Referential boundary: The target chemical should be classified as SN1 OR SN1 >> Alkylation after metabolically formed carbenium ion species OR SN1 >> Alkylation after metabolically formed carbenium ion species >> Polycyclic Aromatic Hydrocarbon Derivatives OR SN2 OR SN2 >> Alkylation, direct acting epoxides and related after P450-mediated metabolic activation OR SN2 >> Alkylation, direct acting epoxides and related after P450-mediated metabolic activation >> Polycyclic Aromatic Hydrocarbon Derivatives by DNA binding by OASIS v.1.3

Domain logical expression index: "g"

Referential boundary: The target chemical should be classified as Class 5 (Not possible to classify according to these rules) by Acute aquatic toxicity classification by Verhaar (Modified) ONLY

Domain logical expression index: "h"

Referential boundary: The target chemical should be classified as Not known precedent reproductive and developmental toxic potential by DART scheme v.1.0

Domain logical expression index: "i"

Referential boundary: The target chemical should be classified as Inorganic chemical OR Known precedent reproductive and developmental toxic potential OR Not covered by current version of the decision tree OR Toluene and small alkyl toluene derivatives (8a) by DART scheme v.1.0

Domain logical expression index: "j"

Referential boundary: The target chemical should be classified as Bioavailable by Lipinski Rule Oasis ONLY

Domain logical expression index: "k"

Similarity boundary:Target: OC(=O)c1cnccn1
Threshold=10%,
Dice(Atom centered fragments)
Atom type; Count H attached; Hybridization

Domain logical expression index: "l"

Referential boundary: The target chemical should be classified as Inclusion rules not met by Skin irritation/corrosion Inclusion rules by BfR

Domain logical expression index: "m"

Referential boundary: The target chemical should be classified as Aliphatic acids and (Met)acrylic acids by Skin irritation/corrosion Inclusion rules by BfR

Domain logical expression index: "n"

Parametric boundary:The target chemical should have a value of log Kow which is >= -0.853

Domain logical expression index: "o"

Parametric boundary:The target chemical should have a value of log Kow which is <= 1.7

Validity criteria fulfilled:
not specified
Conclusions:
Using OECD QSAR toolbox version 3.4 the median Effective concentration (EC50) value for test chemical Pyrazine-2-carboxylic acid on Pseudokirchneriella subcapitata in a 72 hour study was estimated to be 145.27 mg/L on the basis of effects on growth rate.
Executive summary:

Using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the five closest read across substances, the short term toxicity on aquatic algae and cyanobacteria was predicted for target substance Pyrazine-2-carboxylic acid. EC50 value was estimated to be 145.27 mg/l for Pseudokirchneriella subcapitata for 72 h duration. This effect value indicating that the substance Pyrazine-2-carboxylic acid (CAS no. 98-97-5) does not pose a significant hazard to algae and thus consider to be not classified as per the CLP classification criteria.

Description of key information

Using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the five closest read across substances, the short term toxicity on aquatic algae and cyanobacteria was predicted for target substance Pyrazine-2-carboxylic acid. EC50 value was estimated to be 145.27 mg/l for Pseudokirchneriella subcapitata for 72 h duration. This effect value indicating that the substance Pyrazine-2-carboxylic acid (CAS no. 98-97-5) does not pose a significant hazard to algae and thus consider to be not classified as per the CLP classification criteria.

Key value for chemical safety assessment

EC50 for freshwater algae:
145.27 mg/L

Additional information

Four studies including predicted data from validated tool and experimental data from secondary data source for toxicity to aquatic algae endpoint of test chemical Pyrazine-2-carboxylic acid (Cas no. 98-97-5) with relevant read across which is close to target using log Kow as primary descriptor were summarised as follows:

 

Using the OECD QSAR toolbox version 3.4 with log kow as the primary descriptor and considering the six closest read across substances, which indicate the short term toxicity on aquatic algae and cyanobacteria was predicted for target substance chemical Pyrazine-2-carboxylic acid (Cas no. 98-97-5). The EC50 value was estimated to be 145.27mg/l for Pseudokirchneriella subcapitata for 72 h duration. 

 

Similarly, prediction by three different model i.e, Battery, Leadscope and SciQSAR used within Danish QSAR database indicate the short term toxicity on green algae was predicted for test substance  Pyrazine-2-carboxylic acid (CAS: 98-97-5). The average EC50 value was given by the third model i.e, Battery model. On the basis of effects observed in a static freshwater system, the effect concentration EC50 value for the substance Pyrazine-2-carboxylic acid is estimated to be 158.69 mg/l for Pseudokirchneriella subcapitata during 72 hr exposure duration.

 

For the read across substance, Sodium 2-ethylhexanoate (Cas no. 19766-89-3), toxicity test to green algae study was carried out according to OECD Guideline 201 (Alga, Growth Inhibition Test). The study was based on the growth rate effects of the test compound sodium 2-ethylhexanoate (Cas no.19766-89-3)on green algae. And the effect concentration (EC50) was observed to be 500 mg/l and no observed effect concentration (NOEC) was observed to be 130 mg/l at 72 hrs exposure period. (Japan chemicals collaborative knowledge database (J-check), 2017)

For another read across chemical Succinic acid (Cas no. 110-15-6) from robust summary posted to the HPV Challenge Program Dec. 22, 2006, in a static test method, the effect concentration (EC50) of substance Succinic acid in test species Spirulina labyrinthiformis (blue-green algae) was observed to be 120 mg/l for 72 hrs exposure period.  

Thus based on the effects from all studies give the conclusion that test substance Pyrazine-2-carboxylic acid (Cas no. 98-97-5) with effect concentrations in the range 120 to 500 mg/l was likely to be non toxic to aquatic algae at environmentally relevant concentrations and can be considered to be not classified as per the CLP classification criteria.